Theory, technology and assembly of a highly symmetrical capacitive triaxial accelerometer

A highly symmetrical cubic easy-to-assemble capacitive triaxial accelerometer for biomedical applications has been designed, realized and tested. The outer dimensions of the sensor are 5×5×5 mm ³ and the device is mounted on a standard IC package. New aspects of the sensor are an easy assembly procedure, the use of the polymers polydimethylsiloxane (PDMS) as spring material between the capacitor plates and the mass and polyimide (PI) as flexible interconnection layer between the capacitor plates, and the highly symmetrical cubic structure. The mathematical model, technology and assembly procedure of the sensor are described. The measurement results show a good linearity in the output voltage for accelerations up to at least 5 g and a bandwidth of DC >50 Hz. In the x-axis the sensitivity was found to be 175 mV/g which is in good correspondence with the theory. The sensitivity can be increased when the PDMS layer is patterned, which was shown in previous versions of the highly symmetrical triaxial accelerometer